Orf (contagious pustular dermatitis of sheep) is caused by a virus that is communicable to man. The proposed research will investigate the usefulness of a surgical preparation to characterize host-orf virus interactions at the level of the local lymph node in sheep. Chronic cannulation of an efferent lymphatic allows one to have continuous access to virus titers, humoral antibodies and cells draining from a responding lymph node. Quantitative and qualitative morphological differences in the cell populations draining from a local node during the response to virus inoculation will be documented. Cell-mediated immune functions to be tested for include cytotoxicity and viral antigen blastogenesis. The role of antibody and complement dependency for cellular cytotoxicity will be determined when cells in the efferent lymph are mixed with orf virus-infected and 51 chromium labeled autologous, heterologous, and xenogeneic target cells. The nature of surface markers bn cytotoxic cell populations will be determined with the intent to classify them as T cells, B cells, or null cells.